Cannot say of the gun will work but I can tell you that all soldering guns are not the same.
This gun will probably work in the beginning but if you are going to be building packs you want to get something that can reach 800 degree's.
Buy solder from your local hobby store. Do not use what you have. Buy a tube of Deans.
Didn't you just buy this car? Personally, I would save the cash and practice. If you are going to run foams, buy some foams and several good stock motors and that's it. The graphite parts at this stage in the game could only hurt you as they will break much easier than what you currently have on the car.